Topgraded Resources

Calculations

Coefficient of Performance. Note that the Europeans have a more sophisticated Seasonal COP (SCOP) [1]
US has SEER - Seasonal Energy Efficiency Ratio[2]
Heatuing Seasonal Performance Factor - [3]
Cost - note that the above states $7-11k system cost - large value that the owner-builder can create as the hardware involved is only 1/5 of the cost.
Ground Source - tubing install cost is $13-24k according to above video. Extraction is 10-30W/meter of tubing. Water source heat pump is a bit better, and has extraction of 20-60W/meter of tubing.

2ton, 9 HSPF, 17 SEER, $1040 [4]. Has outlets for up to 4 heat exchanger units. One unit comes with the basic package. This one needs to be vacuumed and pumped. DIY versio is precharged for $800 extra. You can set it for freeze proof - which keeps your space at 42F.
Videos for the above: